Java LocalDate toEpochDay Method

Introduction

The Java LocalDate class provides the toEpochDay() method that can be used to convert a date to Epoch Day. The Epoch day count is the number of days that have elapsed since January 1, 1970. In this lab, you will learn how to use the toEpochDay() method and its syntax.

Skills Graph

Set up the Project

To use the toEpochDay() method, we first need to create a Java project. Open the terminal and run the following command to create a directory named "myProject":

mkdir myProject

Now navigate to the project directory using the cd command:

cd myProject/

Create a Java class

In this step, we will create a Java file called DateDemo.java. Run the following command in the terminal to create the file:

touch DateDemo.java

Open the file in a text editor using the following command:

touch DateDemo.java

Implement LocalDate toEpochDay()

In this step, we will implement the toEpochDay() method to convert a LocalDate to Epoch Day.

Add the following code to the DateDemo.java file:

import java.time.LocalDate;

public class DateDemo {
    public static void main(String[] args) {
        // Create a LocalDate object for January 10, 1970
        LocalDate localDate = LocalDate.of(1970, 1, 10);

        // Get the epoch day count for the localDate object
        long epochDay = localDate.toEpochDay();

        // Print the epoch day count
        System.out.println("Epoch Day Count: " + epochDay);
    }
}

Save and exit the file using Ctrl+X, Y, Enter.

Compile the Java file

In this step, we will compile the DateDemo.java file using the javac command. Run the following command in the terminal:

javac DateDemo.java

This will generate a DateDemo.class file in the same directory.

Run the Java program

In this step, we will run the DateDemo program. Run the following command in the terminal:

java DateDemo

This will run the program and output the epoch day count for January 10, 1970.

Test the LocalDate toEpochDay() with a different date

In this step, we will test the toEpochDay() method with a different date. Change the LocalDate object to represent January 15, 2021:

LocalDate localDate = LocalDate.of(2021, 1, 15);

Recompile the program using the javac command:

javac DateDemo.java

Run the program again using the java command:

java DateDemo

This should output the epoch day count for January 15, 2021.

Use the toEpochDay() method to calculate the difference between two dates

In this step, we will use the toEpochDay() method to calculate the difference between two dates in days.

Add the following code to the main method:

// Create two LocalDate objects
LocalDate date1 = LocalDate.of(2010, 5, 10);
LocalDate date2 = LocalDate.of(2020, 3, 15);

// Calculate the difference between the two dates in days
long diffInDays = date2.toEpochDay() - date1.toEpochDay();

// Print the difference in days
System.out.println("Difference in days: " + diffInDays);

Save and exit the file using Ctrl+X, Y, Enter.

Recompile the program using the javac command:

javac DateDemo.java

Run the program again using the java command:

java DateDemo

This should output the difference between May 10, 2010 and March 15, 2020 in days.

Use the toEpochDay() method with the current date

In this step, we will use the toEpochDay() method to get the epoch day count for the current date.

Add the following code to the main method:

// Get the current date
LocalDate today = LocalDate.now();

// Get the epoch day count for today's date
long todayEpochDay = today.toEpochDay();

// Print the epoch day count for today's date
System.out.println("Today's Epoch Day Count: " + todayEpochDay);

Save and exit the file using Ctrl+X, Y, Enter.

Recompile the program using the javac command:

javac DateDemo.java

Run the program again using the java command:

java DateDemo

This should output the epoch day count for today's date.

Use the toEpochDay() method with a leap year date

In this step, we will use the toEpochDay() method with a date that falls on a leap year.

Add the following code to the main method:

// Create a LocalDate object for February 29, 2020
LocalDate leapDate = LocalDate.of(2020, 2, 29);

// Get the epoch day count for February 29, 2020
long leapEpochDay = leapDate.toEpochDay();

// Print the epoch day count for February 29, 2020
System.out.println("Leap Day Epoch Day Count: " + leapEpochDay);

Save and exit the file using Ctrl+X, Y, Enter.

Recompile the program using the javac command:

javac DateDemo.java

Run the program again using the java command:

java DateDemo

This should output the epoch day count for February 29, 2020.

Clean up the project

In this step, we will clean up the project by deleting the DateDemo.java and DateDemo.class files.

Run the following command in the terminal to delete the DateDemo.java file:

rm DateDemo.java

Run the following command in the terminal to delete the DateDemo.class file:

rm DateDemo.class

Summary

In this lab, you learned how to use the toEpochDay() method to convert a LocalDate to Epoch Day. You also learned how to calculate the difference between two dates using the toEpochDay() method and how to get the epoch day count for the current date. Finally, you learned how to use the toEpochDay() method with a date that falls on a leap year.